Resistance contact device for air-blast circuit breakers



Oct. 4, 1966 ZENICHI NAKANO RESISTANCE CONTACT DEVICE FOR AIR-BLAST CIRCUIT BREAKERS 2 Sheets-Sheet 1 Filed Oct. 28, 1965 FIG.

Inuen'fiOQ z h; fiaKeno Fh-roRnEy Oct. 4,1966 ZENICHI NAKANO RESISTANCE CONTACT DEVICE FOR AIR-BLAST CIRCUIT BREAKERS 2 Sheets-Sheet 2 Filed Oct. 28, 1963 FIG. 4

FIG. 3

FIG. 5

IL Il Time In U E FIT O2 Zed-ch naKam United States Patent ()1 RESISTANCE CONTACT DEVICE FOR AIR-BLAST CIRCUIT BREAKERS Zenichi Nalrano, Hitachi-shi, Japan, assignor to Hitachi, Ltd., Tokyo, Japan, a corporation of Japan Filed Oct. 28, 1963, Ser. No. 319,411 Claims priority, application Japan, Oct. 29, 1962, 37/ 46,986 1 Claim. (Cl. 200-148) This invention relates to air-blast circuit breakers and particularly to resistance contact devices therefor.

With multibreak air-b-last circuit breakers for highvoltage use, it is common to insert a resistance in each of the interrupting parts in parallel therewith for improvement of the voltage distribution or for reduced current interruption. Particularly with air-blast circuit breakers of the internal disconnection type, in which the movable member of the interrupting part is restrained in open position for disconnection, it is necessary to disconnect the parallel resistance circuit after the are formed upon opening of the interrupting part has been completely extinguished. The present invention has for its object to provide a resistance contact device which is arranged so that the current flowing through the parallel resistance circuit is interrupted only after the are formed upon opening of the interrupting part has been completely extinguished and in which a substantial insulating distance is obtained between the contacts in the parallel resistance circuit when they are opened.

Description will now be made in detail on the resistance contact device of the present invention with reference to the accompanying drawings, which illustrate one preferred embodiment of the present invention. Details of the interrupting part and its actuating mechanism of the circuit breaker are not shown or described herein as they form no part of the invention. In the drawings:

FIG. 1 is a vertical cross-sectional view of the interrupter chamber of the circuit breaker embodying the present invention showing the interrupter and resistance contacts in closed position;

FIG. 2 is an enlarged vertical cross-sectional view of the resistance contact device of the circuit breaker showing the movable contact in closed position;

FIG. 3 is a view similar to FIG. 2 of the resistance contact device showing parts in positions assumed immediately before the movable contact is moved apart;

FIG. 4 is a view similar to FIGS. 2 and 3 showing the movable contact in open position; and

FIG. 5 is a chart carrying operation characteristics of the movable member of the interrupter and the resistance contact device of the circuit breaker.

Referring to the drawings, the air blast circuit breaker includes interrupter chamber 1 which is always filled with high pressure air. Terminal bushings 2 and 3 extend through the respective end walls of the interrupter chamber in air-tight relation thereto and each carries at its inner end a stationary contact finger 4 or 5, which forms part of the interrupter. Each of the bushings 2 and 3 carries a current terminal (not shown) at its outer end outside of the chamber. Mounted on each of the terminal bushings inside the interrupter chamber 1 is a resistor electrode 6 or 7 which branches from the conductor extending through the terminal bushing. A nozzle type movable member 8 is arranged in bridging relation to the stationary contact members 4 and 5 and includes two tubular portions positioned to contact the respective stationary contact members 4, 5 and each formed with an air orifice (not shown), which is closed when the tubular portions are moved into such contact. A casing 9 is provided to slidably enclose to tubular contacting portions of the movable member 8. A cover plate 10 is arranged to ice close the top of the interrupter chamber 1 and the casing 9 and is formed at the center with a valve port (not shown) communicating with vent holes 11. The operating section includes a cylinder 12 arranged above the vent holes and accommodates a valve operable to open and close said valve port for actuating the movable member 8 of the interrupter and an operating piston for actuating the valve. A control valve 13 is arranged so as to be controlled from ground by way of an insulated conduit to introduce high-pressure air into the space above the operating piston in the cylinder 12 or to discharge the air therefrom for operation of the movable member 8.

Arranged in the interrupter chamber 1 in opposing relation to the respective resistance electrodes 6 and 7 are piston-cylinder assemblies for the purpose described hereinafter, each of which includes a vertically arranged stationary cylinder 14 and a piston structure 15 fitted therein. The piston structure includes a piston body and a piston rod extending downwardly therefrom, as illustrated. A movable contact 16 is supported on the piston rod at its bottom in sliding relation thereto through the intermediary of a pressure spring 18, which is provided for pressing the movable contact against the electrode 6 or 7. A compression spring 17 is arranged in the cylinder 14 beneath the piston body for normally biasing the latter upwardly. The piston 15 carries on its top a disc 19 which serves as a check valve. The piston rod is formed at its bottom with a lateral projection 20. A projection 8a is formed on the movable interrupter member 8 so as to engage the top surface of the lateral projection 20 for the purpose of forcing down the piston structure 15 against the bias of the compression spring 17.

A small aperture 21 is formed through the top wall of the cylinder 14 with a vertical groove 22 formed in the inner wall surface thereof. The piston body carries at its top a C-clip 23 for holding down the check valve or disc 19 against the top surface of the piston body. Also, the piston body is formed with a number of small through apertures 24. The movable contacting piece 16 has lateral lugs 25 held in engagement with the lateral projection 20 on the piston rod for the purpose of preventing the movable contact from falling off the piston structure 15.

The resistance electrode 6 has at its top a contacting portion 6a for contacting the movable contacting piece 16. The body of electrode 6 is formed of a resistance material packed in an insulating sleeve and has an appropriate resistance value. When the interrupter is in closed position, the electrode 6 itself forms a part of the shunting resistance circuit with the movable contact 16 held in contact with the electrode 6.

When high-pressure air is introduced through control valve 13 into the upper space in the operating cylinder 12 above the piston fitted therein, the latter is forced down to move the movable interrupter member 8 into pressure contact with the stationary contact members 4 and 5 so that the pistons 15 in the respective cylinders 14 are each lowered by the projection 8a formed on the movable member 8 to bring the movable contact 16 into pressure contact with the contacting portion 6a on top of the resistance electrode 6, as illustrated in FIGS. 1 and 2. As clearly shown in FIG. 1, the resistance electrodes 6 and 7 in the closed position are in parallel connection with the interrupter including movable member 8 and stationary contacts 4, 5.

The interrupting operation of this circuit breaker is effected under the control of the control valve 13 by allowing the high-pressure air in the operating cylinder 12 to discharge to the exterior thereof. On this occasion, as the drive force normally downwardly urging the operating piston in the cylinder 12 is released, the piston is raised to communicate the interior of the casing 9 for the movable member with the vent holes 11. Consequently, the movable member 8 is driven upwardly by the air pressure in the interrupter chamber 1 to open the interrupter therein. Simultaneously with this, the drive piston 15 is moved upwardly under the bias of compression spring 17 as the downward drive of the movable member 8 previously acting upon the piston 15 is removed. However, the upward movement of the drive piston 15 is extremely slow due to the dash-pot effect of the high-pressure air in the space in the cylinder 14 above the piston body therein. The dash-pot eifect is obtained from the fact that the high-pressure air in the cylinder 14 is allowed to flow out only through the small aperture 21 in the top wall of the cylinder as the apertures 24 in the piston body closed by the disc 19. During the initial portion of the upward movement of the piston 15, the movable contacting piece 16 projecting downwardly under the bias of the pressure spring 18 is held in contact with the contacting portion 6a of the resistance electrode, as shown in FIG. 3. After the drive piston 15 has been moved by a predetermined distance, I (FIG. 2) to place the lateral projection 20 formed on its bottom into engagement with the projections 25 on the movable contact 16, the latter is raised to open the shunting resistance circuit. By this time, the piston 15 rising in the cylinder 14 reaches a position to allow the air in the upper space in the cylinder to escape into the lower space therein through the vertical groove 22 formed in the inner wall surface of the cylinder 14. The rising speed of the piston 15 is thus rapidly increased to suddenly open the resistance circuit. The operating characteristic of the movable contact 16 is represented by the curve B in FIG. 5. On the other hand, the interrupter is designed to operate in two steps and has an operating characteristics as represented by the curve A in FIG. 5. Namely, the movable member 8 of the interrupter is first separated from the stationary contacts by a predetermined distance S and rests there until the are formed between the contacts is completely extinguished when the member 8 is restarted to rise a further distance S to complete its opening travel. In this interrupting operation, the piston 15 for actuating the movable contact 16 in the resistance circuit is started to rise at the same time as the movable member 8 of the interrupter but initially at an extremely limited speed so that the resistance circuit is opened only after the interrupter has been opened, since the piston 15 remains in contact with the resistance electrode 6 under the action of pressure spring 18 during the movement of the piston over the initial distance l and also since the compressed air in the cylinder 14 acts as a dash-pot. After the movement over the initial predetermined distance I, the piston 15 is allowed to move rapidly into the position shown in FIG. 4 owing to the provision of the 'vertical groove 22 in the inner wall surface of the cylinder 14 thereby to ensure the interruption of the resistor current.

In order to restore the circuit breaker, itis required to control the control valve 13 so that high-pressure air is introduced into the cylinder space above the operating piston to lower the latter together with the movable member 8. In this manner, the integral projections 8a on the movable member, engaging with the projections 20 for-med on the respective drive pistons 15, act to lower the latter. On this occasion, each of the drive pistons 15 can be smoothly moved since the air in the cylinder space beneath the piston 15 flows through the apertures 24 into the upper cylinder space while raising the disc 19. Thus, the movable member 8 and movable contacts 16 are lowered simultaneously in such a manner that, first, the movable contacts 16 come into contact with the contacting portions 6a of the resistance electrodes 6, 7 to complete the shunting resistance circuit and then the movable member 8 is pressed against the stationary contacts 4 and 5 to restore the interrupter to its normal closed position. The closed state of the interrupter and the contacts in the resistance circuit is maintained by the air pressure in the operating cylinder 12 acting downwardly upon the operating piston therein.

As apparent from the foregoing, the opening operation of the resistance contact device of the present invention is started with the starting movement of the movable member of the interrupter and then proceeds perfectly independently of the subsequent movement of the movable member. In other words, the movable contacts are moved extremely slowly while maintaining the closure of the resistance circuit under t-he bias of the pressure springs during the initial portion l of their travel and then are moved rapidly. In this manner, the resistance circuit is at all times opened after a constant predetermined length of time, from when the movable contacts have started to operate. In addition, an insulation distance is obtainable between the movable contacts and the resistance electrodes which is comparable to that in the interrupter. Thus, according to the present invention, the interruption of the current flowing through the shunting resistance can be effected in an efiicient and positive manner and the interrupting performance of the air-blast circuit breaker is highly improved, as will readily be appreciated.

What is claimed is:

A resistance contact device for air blast circuit breakers comprising in combination: a pair of movable contacts, stationary contacts in opposing relation to said movable contacts, a pair of drive pistons and piston rods each linked with a respective drive piston supporting one of said movable contacts slidably and a first pressure spring for pressing said movable contact toward said stationary contact, a pair of drive cylinders each including one of said drive pistons, second pressure springs each arranged in one of said cylinders for biasing the piston therein to maintain said movable contacts open; dash-pot arrangements each including first small apertures in each of said drive pistons for controlling drive speed of the drive piston in the initial stages of opening and closing operation of said movable contacts, a washer carried within one side of said drive piston and a second small aperture at the end of the drive cylinder, a movable interrupter member, first projections formed at the tops of said piston rods engagable with corresponding second projections formed on said movable interrupter member to press said movable contacts into contact with said stationary contacts against the biasing force of said second pressure springs in the closing operation; and disengaged with said second projections in the opening operation, vertical grooves formed on the inner walls of said drive cylinders, each of said grooves extending to interlink two divided spaces in the drive cylinder by the drive piston after the are generated at the interrupting part has been extinguished.

References Cited by the Examiner UNITED STATES PATENTS 1,289,649 12/1918 De Camp 200-97 2,717,293 9/1955 Titus et al. 200- 2,911,546 11/1959 Oppel 200148 X FOREIGN PATENTS 346,301 11/1920 Germany. 335,380 9/1930 Great Britain.

ROBERT K. SCHAEFER, Primary Examiner.

KATHLEEN H. CLAFFY, ROBERT S. MACON,

Examiners.

P. E. CRAWFORD, Assistant Examiner. 

